1. Field of the Invention
The invention relates to an arrangement of at least one ultrasound testing head in a test system for the ultrasonic testing of a welding of a tube seam.
2. Description of the Prior Art
When testing the welding seam of tubes for longitudinal errors, especially with tubes having large diameters, it is necessary for some tasks to get as closely as possible to the welding seam. For leading the ultrasound-testing head a support is used, which shows two support-points each on both ends in the peripheral direction. Normally the sound-entrance point is situated with the systems known in the peripheral direction of the tube centric between the support points of the locating arrangement. This has the advantage that the angle of sound entrance once chosen stays the same for all diameters of the tube and the optimal angle of sound entrance can be measured at a device with a plane supporting surface. With this arrangement the possible minimal distance welding seam edge/sound-entrance point is half of the distance of the support points of the locating arrangement.
If the test task requires to get closer to the welding seam edge with the sound-entrance point, the distance of the support points would have to be maximized so much with a locating arrangement and with a centric sound-entrance point, that the front support point seen from the peripheral direction of the tube lies on one side of the welding seam, while the rear support point and the sound entrance point lies on the opposite point of the welding seam. Disadvantages of this arrangement are:
a) The distance of the support points of the locating arrangement needs to be changed to different distances for the sound-entrance point to the welding seam edge, meaning, in some cases, that no indicator optimization by continuous change of skip distance is possible. PA1 b) Seam edge racking can sometimes occur (meaning, different sheet metal heights on both seam sides) which can lead to undefined changes of the angle of the sound-entrance point. PA1 c) In the arrangement described earlier, a belt control with the help of the passing-sound is not possible. PA1 R=radius of the circular cross-section of the tube to be examined PA1 M=center of the circular cross-section PA1 Alpha=angle between the sides (M-scanning device and M-front support point) PA1 x=way of the scanning device (reference point for the angle correction) PA1 x'=distance of the scanning device to the closed tangent situated at the front support point EQU R/(R+x')=cos alpha=(R-x) (1) EQU R2=(R-x)(R+x')=R2+Rx'-Rx-xx' (2) EQU Rx=x'(R-x) (3) EQU x'=Rx/(R-x) (4)